Blue light excitation at room temperature in lead-free double perovskite with Yb doping

Lead-free perovskites are becoming a focal point in the quest for non-toxic and stable materials for optoelectronic applications. Despite this interest, achieving blue light excitation from the lead-free halide double perovskite Cs 2 AgInCl 6 at room temperature remains a significant challenge, hindering their commercial viability. Here, we address this issue by synthesizing the rare earth lead-free double perovskite Cs 2 Ag 0.6 Na 0.4 In 0.8 Bi 0.2 Cl 6 :Yb, which demonstrates visible/near-infrared (NIR) light emission at 598 and 1,000 nm upon blue light excitation at room temperature. We show that this excitation stems from complex interactions between energy level splitting induced by Yb and self-trapped exciton energy levels. Notably, we observe that under blue excitation, the photoluminescence intensity increases with temperature. Furthermore, Cs 2 Ag 0.6 Na 0.4 In 0.8 Bi 0.2 Cl 6 :Yb is integrated into a blue-light-emitting diode, enhancing the conversion efficiency of GaAs solar cells as a down-shifting layer. Ultimately, this research opens new avenues for developing eco-friendly, efficient materials with significant implications for sustainable technology.